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Sabrina Loschonsky Tobias Wacker Simon Waltzer Pier Paolo Giovannini Michael J. McLeish Susana L. A. Andrade Michael Müller 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(52):14630-14634
ThDP‐dependent cyclohexane‐1,2‐dione hydrolase (CDH) catalyzes the C C bond cleavage of cyclohexane‐1,2‐dione to 6‐oxohexanoate, and the asymmetric benzoin condensation between benzaldehyde and pyruvate. One of the two reactivities of CDH was selectively knocked down by mutation experiments. CDH‐H28A is much less able to catalyze the C C bond formation, while the ability for C C bond cleavage is still intact. The double variant CDH‐H28A/N484A shows the opposite behavior and catalyzes the addition of pyruvate to cyclohexane‐1,2‐dione, resulting in the formation of a tertiary alcohol. Several acyloins of tertiary alcohols are formed with 54–94 % enantiomeric excess. In addition to pyruvate, methyl pyruvate and butane‐2,3‐dione are alternative donor substrates for C C bond formation. Thus, the very rare aldehyde–ketone cross‐benzoin reaction has been solved by design of an enzyme variant. 相似文献
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M. Sc. Akash Kaithal Pit van Bonn Dr. Markus Hölscher Prof. Dr. Walter Leitner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):221-226
Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO)2Br[HN(C2H4PiPr2)2]] 1 ([HN(C2H4PiPr2)2]=MACHO-iPr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to “biohybrid” molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C−C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules 相似文献
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